Prediction of vapor-liquid equilibria for supercritical alcohol + fatty acid ester systems by SRK equation of state with Wong-Sandier mixing rule based on COSMO theory

摘要

Vapor-liquid equilibria for supercritical alcohol+fatty acid ester systems were predicted by Soave-Redlich-Kwong (SRK) equation of state with the Wong-Sandier (WS) mixing rules based on an activity coefficient model by Conductor-like Screening Model (COSMO) theory. The predicted systems were methanol + methyl laurate, methanol+methyl myristate, ethanol+ethyl laurate, and ethanol+ethyl myristate systems from 493 to 543 K, near the critical temperatures of methanol (T_c = 512.6 K) and ethanol (T_c = 513.9 K). The excess Gibbs free energies for the mixing rule were determined from the COSMO-Segment Activity Coefficient (COSMO-SAC) model. The universal parameters in COSMO-SAC model were determined by fitting vapor-liquid equilibrium data for alcohol+alkyl acetate systems at low pressures. Predictions for the liquid phase by SRK/WS/COSMO-SAC reproduced the experimental data more accurately than calculations made with SRK/WS/UNIFAC.